1. Field of the Invention
The present invention relates in general to an automotive seat slide device which can slide the seat to a desired fore-and-aft position relative to a vehicle floor, and more particularly to a locking mechanism for the seat slide device so that the seat can be locked at the desired position. More specifically, the present invention is concerned with a biasing structure for biasing a locking pawl operation rod of the lock mechanism in a locking direction.
2 Description of the Prior Art
In order to clarify the task of the present invention, one conventional biasing structure of a lock mechanism in an automotive seat slide device will be described with reference to FIGS. 9 to 14 of the accompanying drawings.
In FIG. 10, there is shown a seat 7 for a motor vehicle, to which the seat slide device 1 is practically applied. The seat 7 generally comprises a seat cushion 5 and a seatback 3. The seat slide device 1 is arranged below the seat cushion 5 to permit the seat 7 to slide forward "F" and rearward "R" relative to a vehicular floor (not shown).
As will be understood from FIG. 9, the seat slide device 1 generally comprises two laterally spaced slide units 9 (only the right side unit is shown) and a lock mechanism 11 incorporated with the right slide unit 9.
As is understood from FIG. 9, each slide unit 9 comprises a lower rail 17 which is secured to a vehicle floor (not shown) through front and rear mounting brackets 13 and 15, and an upper rail 19 which is axially slidably engaged with the lower rail 17. The upper rail 19 has the seat 7 mounted thereon.
The lock mechanism 11 comprises an operation rod 21 which extends along the upper rail 19 and is rotatable about its axis. That is, the operation rod 21 is rotatably held by the upper rail 19 through front and rear brackets 26 and 27. As shown, the rear bracket 27 includes two spaced bearing portions 29a and 29b by which a relatively rear part of the operation rod 21 is rotatably held. Within a space defined between the two bearing portions 29a and 29b, there is arranged a locking pawl 23 that is secured to the operation rod 21 to rotate therewith. A pawl proper of the locking pawl 23 is denoted by numeral 23a in the drawing. The operation rod 21 has a normally bent front part 21a that is equipped with a handle 35.
The lock mechanism 11 further comprises an elongate plate 31 extending along the lower rail 17 and is secured to the same. The elongate plate 31 is formed with a plurality of aligned locking openings 33 with which the locking pawl 23 (more specifically, the pawl proper 23a) is selectively engageable.
A biasing structure is incorporated with the operation rod 21 to bias the same in a direction to achieve the locked engagement of the locking pawl 23 with one of the locking openings 33. The biasing structure employs a biasing spring 25 of coil type, which is disposed about a rear end portion of the operation rod 21. The detail of this conventional biasing structure will be described hereinafter.
When the lock mechanism 11 is in a locked condition as shown in FIG. 9, the locking pawl 23 is kept engaged with one of the locking openings 33 under the force of the biasing spring 25. In this condition, the upper rail 19 (thus, the seat 7 mounted thereon) is locked at a certain fore-and-aft position relative to the lower rail 17 (that is, the vehicle floor).
Thus, when the handle 35 is turned upward in the direction f the arrow "A" in FIG. 9 against the force of the biasing spring 5, the locking pawl 23 is released from the locking opening 33 canceling the locked condition of the lock mechanism 11. Under this released condition, the upper rail 19 is permitted to freely move relative to the lower rail 17.
FIG. 11 is an illustration for explaining the biasing structure of the lock mechanism 11. For clarification of the drawing, the locking pawl 23 secured to the operation rod 21 is not illustrated. As is described hereinabove, the biasing spring 25 is a coil spring disposed about the rear end portion 21b of the operation rod 21 to bias the same in the locking direction, that is, in a direction of the arrow "B" in FIG. 9.
As shown, the biasing spring 25 comprises a multi-turned major portion 25a, a cranked arm portion 25b which projects forward from a front end of the major portion 25a and an inwardly bent portion 25c, which is bent radially inward from a rear end of the major portion 25a. The rear end of the operation rod 21 is formed with an axially extending slit 37.
The biasing spring 25 is properly assembled, when the multi-turned major portion 25a is deeply disposed on the rear end portion 21b of the operation rod 21, the inwardly bent portion 25c is put in the slit 37 and the cranked arm portion 25b is put on an upper surface of the bracket 27, while being twisted by a certain degree against a force produced by the spring 25. When the biasing spring 25 is properly assembled, as described, the operation rod 21 is biased in the direction of a arrow "B", that is, in the direction to achieve the locked engagement between the locking pawl 23 and one of the locking openings 33.
For properly assembling the biasing spring 25, the following assembling steps have been employed, which will be described with reference to FIGS. 12A to FIG. 14C. It is to be noted that FIGS. 12A, 13A and 14A are plan views of the biasing structure of FIG. 11, FIGS. 12B, 13B and 14B are side views of the biasing structure and FIGS. 12C, 13C and 14C are bottom views of the biasing structure.
First, as is seen from FIGS. 12A, 12B and 12C, the biasing spring 25 is loosely put on the rear end portion of the operation rod 21 and slightly turned about the same, and then slightly slid toward the bracket 27 to such a position as to establish a shallow engagement of the inwardly bent portion 25c with the slit 37. In this condition, the cranked arm portion 25b is still separated from s the bracket 27, as is seen from FIGS. 12A and 12C. Then, as is seen from FIG. 12B, with the inwardly bent portion 25c kept shallowly engaged with the slit 37, the cranked arm portion 25b is turned or raised in a direction of the arrow "C" against a biasing force produced by the spring 25. Then, as is seen from FIGS. 13A and 13C, with the cranked arm portion 25b kept raised, the biasing spring 25 is slid toward the bracket 27. During this, the inwardly bent portion 25c of the spring 25 slides in the slit 37 keeping the engagement therebetween. When, as is seen from FIGS. 14A, 14B and 14C, the biasing spring 25 is slid to the frontmost position, the cranked arm portion 25b is released to be put on an upper surface of the bracket 27. In this condition, the inwardly bent portion 25c assumes the deepest position in the slit 37.
Finally, as is best seen from FIGS. 14B and 14C, the slit-provided rear end of the operation rod 21 is caulked to form a caulked end "D". With this caulked end "D", the inwardly bent portion 25c of the spring 25 is tightly retained in the deepest position of the slit 37, and thus the biasing spring 25 is assuredly retained on the operation rod 21.
However, due to its inherent construction, the above-mentioned biasing structure has the following drawback. That is, in order to retain the biasing spring 25 on the operation rod 21, it is inevitably necessary to caulk the slit-provided rear end of the operation rod 21. As is known, this caulking process is troublesome and thus lowers the assembling efficiency of the biasing structure and thus that of the seat slide device.